Modern integrated circuits (ICs) are susceptible to electrical overstress (EOS) events and electrostatic discharge (ESD) events. EOS refers to a situation in which a device, such as an IC or a die, is subjected to excessive voltage, current, or power. ESD refers to a particular type of EOS event involving a rapid transfer of electrostatic charge between two elements in a device. Modern ICs are susceptible to these types of events despite meeting various component-level qualifications such the human-body-model (HBM) test, the machine-model (MM) test, and the charged-device-model (CDM) test.
Often, the occurrence of an EOS event does not result in immediate failure of a device. What typically occurs is that each EOS event degrades some aspect of the device. This degradation can significantly reduce the lifespan of the device. In the usual case, an EOS event leaves behind no physical evidence within the device that the event ever occurred. As such, if the device fails after a shorter than expected lifespan, it is difficult to determine the cause of the failure. Failure analysis is unable, for example, to determine whether the device failed as a result of a manufacturing defect or exposure to one or more EOS events.